Why is my car overheating?

We've all seen the classic car breakdown in a movie, where a character lifts up the hood of a broken-down car and is greeted with steam from an overheating engine. Read on to learn the reasons for car overheating and what to do when your car overheats, plus a few tips to help you with preventative maintenance that can save you the hassle and inconvenience of an overheated engine.

What causes engines to overheat?

Common cooling problems

Hopefully, you will never be in a situation where you have to ask why is my car overheating, but if you do experience an overheated engine, it will probably be one of the following causes.

Improper coolant/water mixture

Engine coolant is sold in concentrated form and premix form from automotive retailers like AutoZone. If you buy the premix coolant you should check to see the temperature range that the premix is specified for and ensure that it matches the climate where you live and drive. If you purchase concentrated coolant you will need to add water and mix it to a certain concentration to achieve the proper temperature range for your climate.

Low coolant

Low coolant level can be caused by cracks in the radiator, loose hose clamps within the system, or a worn-out hose. You can look for small or large puddles of coolant under your vehicle after it’s been parked for several hours if you are attempting to diagnose this issue.

Check out this resource on how to check your coolant level.

Bad Thermostat

Your vehicle has a thermostat in the cooling system that allows water to pass through when engine temperatures rise. If the thermostat is faulty, it won’t allow coolant to flow through and you can experience overheating. Some vehicles even have two thermostats, so check your vehicle documentation if you suspect this issue.

Failed water pump

The water pump on your car pushes water through the engine and cooling system to create the cooling cycle. Water pumps do wear out eventually, so this is a repair that is common with vehicles over 100,000 miles. 

Broken radiator fan

Many older vehicles have belt-driven radiator fans, but almost all newer vehicles use small electric motors to drive the radiator fan. The fan will cycle on and off during driving, depending on the requirements of the cooling system, but if the vehicle is parked and running, the fan should be running if the engine is hot or overheating.

Broken Belt

Many modern vehicles use either the serpentine belt or another belt to drive the water pump. If the water pump belt fails, you will experience overheating quickly.

Low engine oil level

If your engine does not have enough oil to lubricate its parts, then there will be a massive increase in friction and a corresponding increase in heat production. Check your oil level and ensure that it is not black and that it’s full. Extremely black oil is a symptom of oil that needs to be changed.

Symptoms of an overheating car

The first and most obvious symptom of an overheating car will be the engine temperature warning light on the dash. This is a red warning light that looks like a thermometer floating in wavy water. If you see this light, you should pull over immediately and shut off the engine to allow it to cool off.

If you miss the warning light, you may end up with a few of these other symptoms:

  • Steam emanating from under the hood
  • A hot engine hood
  • Thumping sounds coming from the engine
  • Reduced engine power
  • Coolant on the ground underneath the car 

What to do when your car overheats

The first step with you suspect that your engine is overheating is to pull over safely and shut off the engine. If there isn’t a safe space to pull over immediately, shut off the air conditioning and turn the heating up to maximum to draw heat from the engine. Pull over as soon as it is safe to do so, as you could do serious damage to the engine if you continue to drive when it’s overheating.

Once you’ve pulled over, allow the engine to cool with the hood down for a period of time, just in case the engine is very hot or steam is coming out, which could burn you.

Once you’ve allowed the engine to cool and you have opened the hood, find the engine coolant reservoir and if it is a see-through material, check to see what the level is. If you notice that it is low, you may have to add coolant before continuing. Be careful not to take off any radiator caps or open coolant reservoirs when the car is still hot, because this could lead to serious burns.

How Can I Prevent an Overheated Engine?

You’ve learned what causes a car to overheat, but how can you prevent this in the first place? Start by checking your coolant levels regularly and use an antifreeze/coolant tester to ensure that your coolant has the proper concentration. It’s also a great idea to do a visual inspection of your hoses and clamps every few months and perform a coolant flush according to your manufacturer’s recommendations.

Get all your antifreeze and coolant at Autozone. If you need help finding the right fluid for your car’s needs, an associate is always ready to assist.


How do you fix a car that overheats?

Allow the engine to cool off, then check your coolant levels and concentration. If those are both fine, begin to troubleshoot the following 10 causes of overheating.

What are 10 common causes of overheating?

Common causes include poor coolant concentration or low coolant level, failed thermostat, bad water pump, coolant leak, low engine oil level, faulty radiator fan, cracked radiator, loose hose clamp, worn or cracked coolant hose, or a broken belt.

Is it safe to drive a car that’s overheating?

No, an overheating engine is at risk of seizing, which would be a huge repair bill. Stop and assess the situation.

Why is my car overheating but it has coolant in it?

It could be that the coolant concentration is not correct, or you may have a bad thermostat, a failed water pump, broken drive belt, or a bad radiator or radiator fan.

Can low oil cause overheating?

Yes, because the engine oil lubricates all the internal engine parts, which reduces friction and lowers the temperature of the engine.

Can I pour water on my engine to cool it down?

Absolutely not. An engine at operating temperature can be several hundred degrees Fahrenheit and if you pour cold water on a hot engine, you could crack parts and do a lot more damage. 

Advice, how-to guides, and car care information featured on and AutoZone Advice & How-To’s are presented as helpful resources for general maintenance and automotive repairs from a general perspective only and should be used at your own risk. Information is accurate and true to the best of AutoZone’s knowledge, however, there may be omissions, errors or mistakes.

Be sure to consult your owner’s manual, a repair guide, an AutoZoner at a store near you, or a licensed, professional mechanic for vehicle-specific repair information. Refer to the service manual for specific diagnostic, repair and tool information for your particular vehicle. Always chock your wheels prior to lifting a vehicle. Always disconnect the negative battery cable before servicing an electrical application on the vehicle to protect its electrical circuits in the event that a wire is accidentally pierced or grounded. Use caution when working with automotive batteries. Sulfuric acid is caustic and can burn clothing and skin or cause blindness. Always wear gloves and safety glasses and other personal protection equipment, and work in a well-ventilated area. Should electrolyte get on your body or clothing, neutralize it immediately with a solution of baking soda and water. Do not wear ties or loose clothing when working on your vehicle.

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